Current technological and pedagogical developments regarding the applications of Web tools for learning purposes are expected to exert a significant impact on education, since they change the relationship between instruction and learning, inquiry and knowledge construction by extending learning spaces beyond the boundaries of the classroom. Among Web tools, digital format of textbooks enriched with multimedia and digital resources, known as e-books, have captured the interest and the imagination of both educators and instructional designers as a promising idea for the integration of ICT in education. Learning objects are the building blocks of e-books and incorporate multimedia features, hyperlinks, interactivity and search ability. Due to their features of reusability, interoperability, adaptability and scalability, learning objects are expected to enhance the potential of ICT in the next generation of instructional design, development, and delivery. This paper presents the outcomes of a developmental project concerning the construction of learning objects and their integration into computer science (CS) e-books for lower secondary education in Greece. The project was implemented in the framework of Digital School (2010) programme, an ambitious national and EU funded programme, which was administered by the Computer Technology Institute and Press "Diophantus", under the aegis of the Greek Ministry of Education. The members of the development group have worked from distance and implemented the project tasks in a collaborative manner. An open source platform was used to support personal and group work, communication, peer feedback, criticism, ideas interchanging, extending and synthesis, collaboration and material sharing among designers.A collection of 157 learning objects and the related metadata information were constructed and included into the computer science e-textbooks and Photodentro (2013), the Greek National Aggregator of Educational Content. They were innovative digital artefacts of four major categories: • visualisations, e.g. interactive, structured learning objects, which present chunks of information regarding content knowledge directly related to the CS textbooks• micro-activities, e.g. dynamic simulations aiming to support students’ inquiry and construction of efficient mental representations about CS concepts• micro-lessons, e.g. interactive videos which support a short task or a complete activity using general purpose software (editor, spreadsheet, presentations) or programming environments (Logo, Scratch). • open-ended applications, which use a problem-based approach; students explore and test what-if scenarios to discover relationships and improve understanding of specific concepts. The presentation will be structured as following. The first part will address theoretical foundations, instructional design issues and the development method followed. After this, indicative examples of learning objects embedded into the CS e-books and the Photodentro repository will be presented, and students’ learning activities and classroom practices will be outlined. Conclusions will be drawn for educational practice and further research.